Honestly I wouldn't mind realism or fantasy so long as they are in the harem genre and I'm the protagonist. If you're biggest problem in life is that you have too many girlfriends then that is the world I want to live in.

________________"Secrets are what the voices in my head say never to tell until I'm sure no one can stop me." -Mort

I would argue that practically no manga has a realistic world. Take any manga with a (bored/unpopular) boy who meets a (weird/pretty) girl that will change his everyday life, his view on the world, etc. What are the odds of such a girl wanting to be with a boy like that? That's unrealistic in a way that doesn't involve pseudo-japanese countries with monsters or kingdoms with dragons